Refactor tests

I've refactored the tests:
* Split the single class into two - one tests ES directly, the other using the ES appender
* Replaced Thread.Sleep with Retry - which also sleeps but periodically attempts assertions
* Replaced test-base with test-fixture; apparently this is the preferred xunit way to compose setup
* Identified that LogicalThreadContext cause the 'xunit weirdness' so isolated and left that test on ignore; the others passing
* Added ability to debug using Fiddler; change the appSetting to true to enable
* Removed the duplicate LogEvent; instead crafting requests that match the production dto